This invention relates to improvements in a dental handpiece, and more particularly to a dental handpiece having means for opening and closing a chuck which enables a dentist to exchange a dental tool easily.
In a conventional dental handpiece, a cylindrical pusher for a plurality of longitudinal slots is always pushed forwardly against the tapered inner periphery of the chuck so as to hold a dental tool firmly due to the flexibility of the chuck. However, this requires a special tool to displace the cylindrical pusher slidably. The operation of the dental tool by such a special tool is very troublesome for the dentist.
A dental handpiece of the above type is proposed by the Japanese Utility Model Application No. 101,183/1982 (U.S. patent application Ser. No. 509,809 now U.S. Pat. No. 4,493,645), in which the peripherally stepped flat bottom portion of a disc-shaped chucking die is snugly engaged in a radial opening of a cylindrical chuck to firmly hold the cylindrical chuck. The flat bottom portion of the chucking die is in a linearly frictional contact with the outer periphery of the dental tool, but the centripetal holding force of the cylindrical chuck is so small that the dental tool is not centripetally, firmly held in the cylindrical chuck, thus easily wearing the chucking die.